1,721,010 research outputs found
Solid-State NMR Characterization of the Insertion of Cobalt into Aluminosilicate Materials
No full textA 29Si-27Al magic-angle spinning NMR study of natural silica glass from the Libyan Desert (Egypt)
No full textSamples of impactite glass, known as Libyan Desert Glass (LDG), were analyzed by NMR MAS in order to study the coordination of silicon and aluminum. In all samples, silicon was observed in a fourfold coordination. A very small amount of aluminum in fourfold, fivefold and sixfold coordinations was also observed in the three studied samples. The occurrence of five and six coordinated aluminum may be due to high pressure effects or due to the presence of Al-enriched micro-domains
Impact of lignite on pedogenetic processes and microbial functions in Mediterranean soils
No full textSilica-zirconium phosphate-phosphoric acid composites: preparation, proton conductivity and use in gas sensors
No full textSolid state and solution structural studies of silver(I) cyclic complexes bearing the (Bzim)Ph2P ligand
No full textCyclic silver(I) compounds having a [mu-(Bzim)Ph2PAg](2)(2+) unit ((Bzim)Ph2P 1-benzyl-2-imidazolyldiphenylphosphine) and NO3- (I), BF4- (II), and B[3,5-(CF3)(2)C6H3](4)(-) (III) as counterions were characterized in the solid state by X-ray crystal structure determinations (I, II), and in solution by H-1-, C-13-, F-19- and P-31-NMR spectroscopies. The crystal structure of complex [mu-(Bzim)Ph2PAg(NO3)](n) (n = 2, 4) (I) (triclinic, space group (no. 2), a = 15.118(5), b = 17.755(3), c = 14.123(4) Angstrom, alpha = 90.23(2), beta = 111.67(2), gamma = 85.92(2)degrees, Z = 2) shows two conformers A and B in the unit cell. The conformer A consists of a tetranuclear species formed by two [mu-(Bzim)Ph2PAg](2)(2+) moieties, related by a center of symmetry, bonded together by two bridging nitrate anions. The nitrate anions are coordinated to the sliver atoms in an unusual fashion. The conformer B is a dinuclear species where the silver atoms present in the eight-membered ring complete their tetracoordination with two chelate nitrate anions. The crystal structure of complex {[mu-(Bzim)Ph2PAg(BF4)](2)}(infinity) (II) (monoclinic, space group P2(1)/c (no. 14), a = 11.563(3), b = 8.353(4), c = 26.188(7) Angstrom, beta = 95.88(2)degrees, Z = 2) consists of infinite chains of the dinuclear cyclic silver moieties held together by BF4- bridging anions. The low temperature experimental and simulated P-31-NMR spectra of complexes I-III show complex apparent doublets of multiplets due to the resonance of the spin systems of the three isotopomers of the silver atoms present in the cyclic units. The interionic solution structure of complex II was investigated by F-19{H-1}-HOESY NMR spectroscopy. In methylene chloride solution the BF4- anion is not more coordinated to the silver(I) atoms as in the solid state, and it is localized in between the phenyl and benzyl groups of the ligand. (C) 2000 Elsevier Science S.A. All rights reserved
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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